1. Field of the Invention
The present invention relates to carts, dollies, hand trucks, and the like, and particularly to a hand truck brake serving to prevent a hand truck from rolling on the tread of a step while negotiating steps or stairways.
2. Description of the related art
Hand trucks, carts, dollies, and similar articles of equipment are commonly used to transport large and bulky objects (e.g., furniture, office equipment, etc.) over relatively short distances, as to or from a delivery truck or within a building structure. Most such hand trucks and the like are manually operated, i.e., they have no additional motive power (e.g., electric motor, etc.). However, a subclass of such hand trucks is configured or adapted for climbing and descending stairways, most of these devices including some form of motive power.
One common need of all such devices, whether powered or non-powered and whether specially adapted for use on stairs or not, is the need to provide some form of braking action to prevent the device from rolling from a step when negotiating steps or stairways. This is conventionally achieved by the operator of the hand truck, who manually holds the truck to prevent it from moving. In practice, this can be difficult at times, depending upon the diameter and relative location of the wheels of the truck, the fore and aft width of the tread of the stairs, whether there is any slope to the stairway tread(s), and other factors. At times, it may require considerable strength to prevent a loaded hand truck from dropping down the stairs if the centers of the wheels are even slightly beyond the nose of the stairway tread. Even when the hand truck is momentarily stable on a stairway tread, it takes only a moment of inattention and slight movement to cause the hand truck to roll beyond the nose of a stairway tread and proceed down the stairway or steps. Even though powered devices configured for negotiating stairways have considerable mechanical advantage limiting the rotation of the wheels when the motor is stopped, they still may roll to some degree against such mechanical advantage, and they may roll freely if the motor and/or driveline are disengaged from the wheels.
As a result, a number of braking devices have been developed in the past for the wheels and/or casters of hand trucks, dollies and carts and the like. One example of such is found in German Patent No. 3,934,234, published on Apr. 18, 1991, which describes (according to the drawings and English abstract) a “wheelbarrow” or hand truck having two sets of wheels to assist in drawing the truck up and over the nose of each stairway tread. The wheels have ratcheting brakes that allow rotation in only one direction to prevent them from rolling down a set of steps. The ratchet brakes are controlled by the operator, who actuates a lever at the top of the hand truck frame.
Another example of a hand truck or cart configured for negotiating stairways is found in German Patent No. 10,113,635 published on Dec. 5, 2002. This document describes (according to the drawings and English abstract) a “trolley” or hand truck having main wheels in a “star wheel” configuration, i.e., a series of small wheels located at the distal ends of a series of radial arms, the arms and wheels rotating about a common single axis. Manually controlled brakes are provided to prevent rotation of the “star wheel” assembly and of the forwardly disposed casters.
Thus, a hand truck brake solving the aforementioned problems is desired.